The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
Free Health Calculator Tools for UK Adults
If you're looking for a reliable health calculator to assess your weight, BMI, or weight loss potential, MyWeightCheck offers free, easy-to-use tools aligned with NHS guidance. Whether you need to convert kilograms to stone, calculate your BMI, or estimate weight loss outcomes with GLP-1 medications, our calculators provide instant, accurate results in UK measurements. All tools are designed specifically for UK adults and follow current NHS health thresholds, making them practical for managing your health at home or with your GP.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
What Health Calculators Can Tell You
Health calculators are simple tools that use your personal data—weight, height, age, and sometimes other factors—to give you health insights aligned with NHS guidance. Our free calculators on MyWeightCheck include:
- BMI Calculator — instantly calculates your Body Mass Index and shows which NHS weight category you fall into (healthy weight, overweight, or obese)
- Weight Converter — converts between kilograms, stone, and pounds—essential since UK adults use stone but NHS clinical records use kilograms
- GLP-1 Weight Loss Calculator — estimates potential weight loss if you're considering prescription weight management medications like Mounjaro or Wegovy, based on clinical trial data
- Progress Tracker — logs your weight over time and shows your progress visually
Each calculator uses evidence-based formulas and NHS thresholds, not guesswork. Results are instant and confidential.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Why Use Our Free Calculators?
Using a free health calculator gives you a baseline understanding of your health without cost or appointment delays. You can check your BMI anytime, convert between measurement systems, or explore what weight loss might look like with medical support. Our tools are designed for UK adults—we use stone and pounds, NHS BMI categories (with lower thresholds for South Asian and Black African heritage), and current UK health guidance.
Results from our calculators can start conversations with your GP. If your BMI suggests you're overweight or obese, your GP can discuss lifestyle changes or, if appropriate, refer you to specialist weight management services or discuss prescription options like Wegovy or Mounjaro. These calculators are informational only—they don't diagnose or prescribe, but they empower you with knowledge.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Is a BMI calculator accurate for everyone?
BMI is a useful screening tool aligned with NHS guidance, but it has limitations. It doesn't distinguish between muscle and fat—athletes may have a high BMI but low body fat. BMI is also less accurate for elderly people, during pregnancy, or for very short adults. Use our BMI calculator as a starting point, then discuss your results with your GP, especially if you have significant muscle mass or other health concerns.
Can I use these calculators if I'm from a South Asian or Black African background?
Yes. Our BMI calculator applies NHS-recommended lower thresholds for adults of South Asian, Chinese, Black African, and Black Caribbean heritage. These groups face higher cardiovascular and diabetes risk at lower BMI levels, so NHS guidance recommends assessing health risk from a BMI of 23 (vs 25 for other adults). The calculator adjusts automatically based on your heritage.
What does the GLP-1 weight loss calculator show?
The GLP-1 calculator estimates potential weight loss based on clinical trial data for medications like Wegovy (semaglutide) and Mounjaro (tirzepatide). It uses results from the STEP and SURMOUNT trials to project weight loss at different doses. Important: these are average estimates only. Individual results vary significantly, and weight loss medication must be prescribed by a licensed healthcare professional following clinical assessment.
Can I use these calculators instead of seeing my GP?
No. These calculators are informational tools only—they don't replace professional medical advice. If your calculator results suggest you're overweight or obese, or if you're interested in weight loss medication, book an appointment with your GP. Your GP can discuss your overall health, family history, and what options may be suitable for you personally.
Are these calculators free and secure?
Yes. All MyWeightCheck calculators are completely free to use, and no registration is required. We don't collect personal data—your results are calculated instantly in your browser and never stored on our servers. You can use the tools with confidence, knowing your privacy is protected.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.